Method and apparatus for coring



W. D. MOUNCE METHOD AND APPARATUS FOR CORING Filed April 12, 1939 Decgz,1941.

FIG. 2 FIG. 3..

BY 91N ENTOR W ATTORNEY.

FIG- .1

f panying *drawingl in which Patented Dec. 2, 194i Urrea lsfr-Ares PATENMETHOD AND APPARATUS FOR COR-ING Whitman D. Mounce, Houston, Tex.,assignor to Standard Oil Development Compamya corporation of' DelawareApplication April 12, 1939, SerialNo. 267,423

` 9 IClaims. (Cl. Z55- 1.8)

The present invention is directed to a method for taking samples in theform of cores from bore holes and to an apparatus suitable for usev eryof a sample from a borehole free from contamination with drilling uid.

An additional object of thepresent invention is the provision of themethod and means lfor the cutting of an uncontaminated core in a borehole and the delivery of said core to thesurface, while maintaining itunder the pressure of the forma-v tion from which it was cut.

Further objects y and advantages will appear from the followingdescription vof the accom- Fig; 1 is a, vertical section through acuring i deviceaccording `to the present .invention in a bore hole withthe partsv in a position which they jassume before coring is begun;

Fig. 2 is asimilar view with the parts in the position they assumeduring the coring operation,

,f Fig. 3 is a similar view,y showing the position of the parts at thecompletion of the coring operation.

. Referring to the drawing in detail, numeral I designates a.v bore holewhich has been drilled into the earth through earth section 2 to a pointjust short of formation 3 which is to be sampled.`

This hole is filled with drilling fluid 4. In the practice ofthe presentinvention, a quantity 5 of mercury or other Water-insoluble liquid,having,

a specific gravity heavier than that of the drilling fluid, is depositedat the bottom of the bore hole, and a coring device is introduced intothe bore hole. tagesof the present invention, the coring device y shouldbe one which is sealed off from the liquid completed and before the openend of the coring device is lifted out of the mercury.

In Fig. l is shown a core barrel 6 carried by a drill stem 1.

The barrel 6 has at its upper end a threaded inlet nipple in which isarranged a valveV V9. To the, lower end of barrel 6 is secureda cylinderIll having a shoulder II intermediate its ends. Mounted on` the upperside of this shoulder is a flap valve I2 which is normally held insealing position vby a spring I3. Below and spaced from this shoulder isa second shoulder` I4, on the upper angular face' of which are pivotedpawls I5 which are wedge-like in shape and are mounted on stub shafts IB.and may'have their pointed ends spring-pressed toward the axis of thecenter of the cylinder Il).

The cylinder I0 carries a cutter head Il which is provided at its loweredge with serrations I8 suitably shaped and sharpened to serve as corecutters. `Between the cutter head I1 and the lower end of cylinderv I0is carried a disk I9 held in place by a washer 29 which is adapted toseat in a suitable recess in the end of j cylinder I0. This disk is madeof a soft metal or other material capable of being ruptured by thevupward movement of a core through the central passage 2| of the cutterhead. Immediately below the disk are radial passages 22, the purpose ofwhich will be hereinafter explained. Also the central passage of thecutting head, as well as the lower end of cylinder I0, is provided withlongitudinal grooves 23, spaced from each other around its periphery,for the purpose hereinafter specified. In the use of the corng devicedescribed above, valve 9 is opened at the surface and the interior ofthe core barrel including cylinder I 0 is filled In order to secure thefull advanwith mercury or other heavy liquid as previously defined. Thisserves to prevent the rupture of the disc I9 by the bore hole fluidpressure before the formation 'to be sampled isreached. The assembly isthen lowered into the well until vthe cutter head reaches the mercury atthebottom. As the assembly is further lowered, the `mercury forces .anydrilling fluid in the central passage of the cutter head out through theradial passages 22, which, in practice, may be so arranged that nodrilling mud will remain in the central passage. Thecoring operation isthen begun.

As` the core begins vto move up through the central passage of -thecutting head, it breaks the disc 20, moves the pawls I5 into theposition ference in` density between the core and the mercuryV in thebarrel causes the f ormer to rise to the top of barrel 6, disengaging apvalve l2 and allowing it to be closed by spring I3. Since the greatestpressure in the bore hole will be at its bottom, and since, when apvalve I2 was closed, the interior of the barrel was in pressureequilibrium with the bore hole, the ap valve will be held securely inclosed position by the pressure inside the barrel during the upwardmovement of the assembly -to the surface.

When the assembly reaches the surface, the barrel 6 is detached from thedrill stem and the nipple 8 is secured to an analytical apparatus. Thevalve 9 is then opened so that any volatile constituents which wereliquid at the formation pressure, butwould vaporize upon a reduction ofpressure, will leave the core and pass into the analytical apparatus.When the volatile constituents have been recovered, the cylinder I canbe severed from the barrel 6 and the core recovered and analyzed.

It will be understood that the above described apparatusis not necessaryto the performance of the method of the present invention. Otherpressure core barrels, such as that described in co-pending applicationSer. NO. 242,211, iiled November 25, ,1938, entitled Pressure coringdevice, can also be employed. Furthermore, the coring device need not beof the pressure type, but can be any of the conventional coring deviceswhich, when used according to the method of the present invention, willdeliver a much less contaminated core than when used in the conventionalmanner. On the other hand, the cori-ng device described above cannotfulll its function of delivering a core under the pressure of theformation from which it was obtained, unless it is used in conjunctionwith a liquid of heavy specific gravity in accordance with the method nof the present invention.

.advantageous to deposit the mercury or other heavy uid in the borehole, beforethe ordinary drill bit is removed, and to drill a few feetinto the surface Without mud circulation. The-object of this step is toremove that portionV of the formation which might be contaminated by thedrilling fluid. Then the drill stem is removed and the conventionaldrill head replaced by the coring drill head described above.

It may also be desirable to circulate drilling fluid in the bore holeduring the coring operation and, for this purpose, ports 24 can be provided in the drill stem just aboyee the core barrel.

It will be understood that th specic embodiment described above ismerely illustrative of the present invention. Changes in size and shapeand arrangement of parts are contemplated within the scope of thisinvention.

The nature and objects of the present inven tion having been thusdescribed and illustrated. what is claimed as new and useful and isdesired to be secured by Letters Patent is:

1. AA method for securing a core at the bottom of a bore hole containinga drilling fluid which comprises introducing into the hole a liquidimmiscible with the drilling fluid and of greater specific gravity thanthe drilling uid, whereby a layer of said .liquid is formed at thebottom of the bore hole, introducing a coring device into the, borehole, conducting the coring operation beneath the layer of introducedliquid, and withdrawing the core produced.

2. A method for securing a core at the bottom of a bore hole containinga drilling uid which comprises introducing into said bore hole a liquidheavier than the drilling fluid and immiscible therewith, whereby alayer of said liquid is deposited at the bottom of said bore hole,introducing into said bore hole a coring device carrying a core barrelsealed from the liquid in the bore hole, maintaining 4said chamber insealed condition until the coring operation is begun beneath said layerof heavy liquid, completing the 4coring operation beneath said layer ofheavy liquid, sealing said chamber while the open end of saidcoring'device is still beneath said heavy liquid, and returning saidchamber to the surface. t

3. A .coring device comprising a core barrel adapted to be secured to adrill stem, a cutter head carried by said barrel having a centralpassage adapted to receive a core, a valve between said central passageand the interior of the core barrel adapted to be opened by the movementof said core into said barrel, means for cutting off a desired length ofsaid core from the formation, means for raising the cut-off portion ofsaid core into said barrel, thereby disengaging it from said valve, andmeans for normally holding said valve in closed position.

4. A coring device comprising a core barrel adapted to be secured to theend of a drill stem, means for sealing the upper end of said barrel fromthe interior of said drill stem, a drilling head secured to said barrelhaving a central passage for the receipt of a core, afrangible diskacross said passage normally sealing the lower end of said barrel and avalve arranged in said barrel above said disk adapted to remain normallyin closed position and to be opened by the movement of a core upwardlythrough said passage.

5. A coring device comprising a core barrel adapted to be secured to theend of a drill st'em, means for sealing the upper end of said barrelfrom the interior-of said drill stem, a drilling head secured to thelower end of said barrel having a central passage for the receipt of -acore, a frangible disk arranged across said passage to normally seal thelower end of said barrel, a valve arranged in said barrel above saiddisk adapted to normally remain in closed position to seal olf the lowerend of said barrel and to be opened by the movement of a core upwardlyintosaid barrel, and means between said valve and said disk for cuttingoff a core.

6. A coring device comprising a core barrel adapted to be secured to theend of a drill stem, a nipple on the upper end of said barrel, a valvein said nipple, a drilling head carried by the lower' end of said barrelhaving a central passage for the receipt of a core, a frangible diskarranged across said passage `normally sealing th'e lower end of saidbarrel, a flap valve arranged in said barrel above said disk adapted toseal the lower end of said barrel, spring means for normally holdingsaid valve in closed position, and cutters arranged in saidbarrelbetween said fiap valve and said disk for severing a coreafrom theformation being tested.

7. A coring device comprising a core barrer adapted to be secured to theend of a drill stem. means for sealing the upper end of said barrel fromthe interior of said drill stem, a drilling head secured to said barrelhaving a central passage for the receipt of a core and a frangible diskarranged across said passage for sealing the lower end of said barrel,said disk being arranged to be broken by the core.

8. A coring device comprising a core barrel adapted to be secured to theend of a drill stem, means for sealing the upper end of said barrel fromthe interior of said drill stem, a drilling head secured to said barrelhavingA a central passage for the receipt of a core, a frangible diskacross said passage normally sealing the lower end of said barrel, avalve arranged in said barrel above said disk adapted to remain normallyin closed position and to be opened by the movement; of a core upwardlythrough passage, and means for raising a cut-oil portion of a core intosaid'barrel, thereby disengaging it from said valve.

9. A coring device comprising a core barrel adapted to be secured to theend of a drill stem. a drilling head secured to said barrel having acentral passage for the receipt of a core, means normally sealing in afluid-tight manner the interior of said core barrelvfrom said passageand adapted to be rendered inoperative as a seal by the core after thecoringoperation has begun and separate means for resealing said barrelfrom said passage ina fluid-tight manner after the completion ofthevcoring operation.

WHITMAN D. MOUNCE. i

